Michael Gallup likely suffered a torn left ACL in the second quarter of the Dallas Cowboys' 25-22 loss to the Arizona Cardinals on Sunday afternoon.
Jerry Jones said Gallup will undergo an MRI on Monday to confirm the extent of the injury, which was suffered on a touchdown catch.
Gallup is scheduled to be an unrestricted free agent after the season.
"Feel terrible for Michael," Mike McCarthy said. "Obviously made a huge play, but you could see just the way he came down."